1. Field of the Invention
The present invention relates to optical readers in general and particularly to an optical reader configured to change operating modes depending on characteristics of images in the reader""s field of view.
2. Background of the Prior Art
Prior art optical readers are sometimes configured to operate in a xe2x80x9ccontinuous scan modelxe2x80x9d so that bar code symbols and other indicia presented to the reader are automatically decoded or otherwise recognized without manually activating a control element such as a trigger to commence indicia recognizing activities.
A continuous scan operating configuration requires repetitive illumination flashing of an LED array in the case of an image sensor based optical reader and repetitive laser scanning in the case of a laser scan engine based optical reader. Repetitive flashing illumination or laser scanning requires a high level of energy consumption and can result in premature component degradation. Furthermore, the repetitive illumination or laser scanning has been observed to be highly distracting to users of such optical readers configured to continuously scan image data.
U.S. Pat. No. 5,550,366 describes a system for automatically activating image scanning in a portable bar code reader when the presence of a bar code in a target area is detected. However, the detection of a bar code in the target area is carried out on a period basis and requires for the detection activation of a high radiance source of illumination. Accordingly, the system is not responsive in real time to an object being moved into the field of view of the reader, and the high radiance illumination required for operation of the system remains a source of distraction.
There is a need for an optical reader which is configured to automatically and in real time decode or otherwise recognize machine readable indicia that is presented to the reader without manual activation of a control element to commence recognition operations.
According to its major aspects and broadly stated, the invention is a method for operating an optical reader so that control of the reader depends on image information being generated by the optical imaging element, such as an image sensor, of the reader.
In one embodiment, the reader control unit analyzes image information being generated by the imaging element and changes the mode of operation of the reader if the image information indicates that machine readable indicia, such as bar code symbols or a text character, is in the field of view of the reader. Normally, analysis of image data includes the step of detecting for edges, or edge transitions in the image information. If the control unit determines that the image information includes more than a predetermined number of edge transitions, then the control unit imparts appropriate control over various reader elements to change the mode of operation to the reader.
When the control unit determines that machine readable indicia is in the field of view of the imaging element then the control unit may change the mode of operation of the reader from a first mode, wherein the reader does not operate to decode or otherwise recognize machine readable indicia to a second mode, wherein the reader actively attempts to decode or otherwise recognize machine readable indicia. The second mode may be characterized, for example, by an increased illumination of the field of view, and/or by the activation or enhancement of decoding algorithms being operated to process captured image data and/or by the activation or enhancement of optical character recognition (OCR) algorithms being operated to process captured image data.
The method may be utilized with any type of optical reader, including a basic hand held bar code reader, a multi functional data collection unit having a keyboard, display, and imaging element, a scan stand optical reader, or a fixed mount optical reader mounted to generate image information corresponding to articles which are manually or automatically moved across a point of transaction.
The method may be utilized with an optical reader to supplement or replace the function normally provided by a trigger switch. In most hand held optical readers a trigger switch is manually depressed to commence decoding or recognition operations of the reader. An optical reader programmed in accordance with the invention may commence decoding and/or recognition operations automatically upon the detection of machine readable indicia in the field of view of the reader without a trigger being depressed.
These and other details, advantages and benefits of the present invention will become apparent from the detailed description of the preferred embodiment herein below.